Bayesian network for assessing a single database ‘hit’. Structure of a Bayesian network for evaluating a correspondence (M1) between the profile of a crime stain and that of a sample from a suspect when the suspect is on a database along with n−1 other individuals whose DNA profiles do not correspond. The size of the population of potential offenders is N. Among the N individuals, n (with n<N) are on a database. The node H has three states: ‘the suspect is the source of the crime stain’ (H1), ‘the second individual in the database is the source of the crime stain’ (H2), and ‘the source of the crime stain is among the N−n(here, n=2) individuals outside the database’ (). The corresponding genetic feature occurs in the population with rate γ. The node X2is binary and represents the proposition according to which the profile of individual 2 (in the database) does not correspond to the crime stain.